Comparison Of Porphyry Geological Features Of Yidun Arc Island In Sanjiang Region

Sanjiang Yidui island arc is located in the Indian plate and the Eurasian plate transfer position. And is formed by the Bayan Har, Qiangtang and Lhasa three plate tectonic systems interact with multi-phase movement and multi-stage mineralization characteristics. These complex geological activities have a rich diversity of tectonic evolution and mineralization conditions, thereby creating the geological condition of Sanjiang region polymetallic deposits.In recent years, many scholars have done many studies of scientific research of Yidun island arc orogenic belt, show that the difference of Yidun arc orogenic belt in different segments of Sichuan and Yunnan segments in diagenesis, stress conditions, and other aspects of the geological background. The geological data shows that Yidun arc from north to south mainly volcanic hydrothermal deposits-VMS deposits-porphyry deposits. But recent studies have found northern Yidun arc still exist porphyry copper deposit(Changdagou, etc). North and south section of Yidun arc are sub-volcanic hydrothermal deposit, while the middle is essentially VMS deposits, so to macro-formed symmetrical north-south trend, and the northern section of the porphyry copper deposit on certain properties and also similar with adakite nature, thus indicating the northern island arc section may also be present with similar geological setting compare to the southern section. So compared predecessors' studies and experiments, we use geochronology, petrology and rock chemistry methods to identify similarities and differences Yidun island arc of the Sichuan and Yunnan section of the attempt from the same and identify the impact of mineralization differs from the distribution of its differences, differences in scale factors mineralization and metallogenic geological conditions differences, thus provide some help to prospecting potential.Through the use of the method U-Pb zircon LA-ICP-MS collected samples dating measured Yidun northern section Shiqu- Garze porphyry body and the middle segment Derong- Xiangcheng porphyry with previous measurements of the southern section of the Gezan Island arc porphyry within the allowable range of geological time is basically in the same period, Shiqu- Garze segment dating mainly in the range of 213 ~ 216 Ma, Litang section dating mainly in 216 ~ 220 Ma, Gezan Island arc segment measured mainly 206 ~ 228 Ma. Petrological characteristics of the rock show that although they are both porphyry body, but in the rock composition there are some differences. Shiqu- Garze segment porphyry body from Peraluminous-metaluminous neutral to slightly acidic porphyry, Litang segments are metaluminous-acidic aluminum mainly granodiorite porphyry, Gezan island arcs are based peraluminous neutral diorite. Thus this three sections porphyry rock lithology still exist some differences. This may be invaded by the upper tectonic stress, the late magma or a variety of geological processes like- effects caused by contamination. From geochemistry aspects, Yunnan and Sichuan segment of the most obvious feature is rare in a standardized curve as a whole shows a positive Eu anomaly enrichment may indicate partial melting, the molten plagioclase resulted melt Eu positive anomalies. Trace elements in a standardized curve that LILE elements Ba, Sr were significantly enriched, Th were negative anomaly, with a clear adakite geochemical characteristic.